We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr_14−xCa_xCu₂₄O₄₁ (SCCO) using Cu L₃-edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with high (x = 12.2) and without (x = 0) Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2 T) excitations (x = 0) to weakly-dispersive gapped modes at an energy of 280 meV (x = 12.2). Density matrix renormalization group (DMRG) calculations of the RIXS response in the doped ladders suggest that the flat magnetic dispersion and damped excitation profile observed at x = 12.2 originates from enhanced hole localization. This interpretation is supported by polarization-dependent RIXS measurements, where we disentangle the spin-conserving ΔS = 0 scattering from the predominant ΔS = 1 spin-flip signal in the RIXS spectra. The results show that the low-energy weight in the ΔS = 0 channel is depleted when Sr is replaced by Ca, consistent with a reduced carrier mobility. Our results demonstrate that off-ladder impurities can affect both the low-energy magnetic excitations and superconducting correlations in the CuO₄ plaquettes. Finally, our study characterizes the magnetic and charge fluctuations in the phase from which superconductivity emerges in SCCO at elevated pressures.

我们使用 Cu L ₃边缘共振非弹性 X 射线散射 (RIXS)研究了 Sr _14−x Ca _x Cu ₂₄ O ₄₁ (SCCO)的准一维 (q-1D) 梯形子系统中的磁激发。通过比较具有高 ( x  = 12.2) 和没有 ( x = 0) Ca 含量的动量分辨 RIXS 光谱 ，我们跟踪磁激发从集体双三元 (2 T) 激发 ( x  = 0) 到弱-能量为 280 meV ( x = 12.2)。掺杂梯子中 RIXS 响应的密度矩阵重整化组 (DMRG) 计算表明，在x  = 12.2 处观察到的平坦磁色散和阻尼激发分布源于增强的空穴定位。这种解释得到了偏振相关 RIXS 测量的支持，我们将自旋守恒ΔS  = 0 散射与 RIXS 光谱中的主要ΔS = 1 自旋翻转信号分开。结果表明， ΔS中的低能权重 = 0 当 Sr 被 Ca 取代时，通道耗尽，这与降低的载流子迁移率一致。_{我们的结果表明，梯外杂质会影响 CuO 4}薄片中的低能磁激发和超导相关性。最后，我们的研究表征了在高压下 SCCO 中出现超导性的相中的磁和电荷波动。